Are the expressions of sight draft , time draft , usance draft and letter of credit adequate terms to express the different methods of payment ?   No . These terms need to be amplified .   What if the sale is made on the basis of sight draft ?   Then the shipping documents have to be attached . That way , both parties confirm the documents that will accompany the draft and constitute evidence of shipment in compliance with the contract terms .   Therefore , we must be very careful in building up clear expressions and complete understanding on both sides of trade .   Yes , that's very important . 